1. Field of the Invention
The present invention relates generally to a wheel lift attachment for a towing vehicle, and more specifically to a hydraulic wheel lift device suitable for use on a wrecker truck and other tow vehicles.
2. Discussion of the Prior Art
The lack of traditional full transverse axles in new foreign and American cars has rendered once commonplace axle tow connections difficult and dangerous for these cars. Also, recent changes in bumper design, including shielded bumper constructions and shock-resistant bumper mountings, have eliminated the traditional bumper-tow connection points and provided materials that are damaged by the pulling of a tow hook or chain. As a result, recent vehicle lift designs have been developed that are oriented to engage the underside of a vehicle frame, or the front or rear wheels of a vehicle. These designs avoid potential frame and bumper damage resulting from the traditional towing connections.
Tow connections in accordance with the recent designs, however, require precise alignment of the tow truck with the vehicle to be towed. On an empty street with a sufficient amount of maneuvering room, proper alignment is a relatively easy task. In crowded lots and along curbsides, where heavy traffic restricts movement, the new designs prove to be cumbersome and fail to give the tow operator the same flexibility that the chain and hook-type systems provided. Further, the more recent designs are not adapted to provide fully automatic connections, thus forcing the driver to leave the cab to hook and unhook the vehicle to be towed.
PETERSON, U.S. Pat. No. 3,484,817, for example, discloses a vehicle lift for a wrecker truck which employs manually deployable fork elements. In operation, a lift-boom attached to the tow truck, is lowered and a pair of folded wheel forks are manually unfolded by the operator. Support rods, located at the distal ends of the forks, are then manually removed from the forks, and the tow truck backs the lift forks toward the vehicle to be towed until the forks surround the wheels. In this position, the support rods are replaced, forming rectangular frames whose longitudinal sides are shorter than the diameter of the tire. The forks and vehicle are then raised by the lift-boom, and the vehicle is towed away. The forks, however, must be precisely aligned with the tire, requiring the operator to back up the forks within about a half-foot from the center line of the tires. Further, the tow operation requires at least three manual steps: two before the wheels are engaged and one after the wheel has been engaged.
HARING, U.S. Pat. No. 4,034,873, discloses a towing sling which can be placed under a tire without the need to raise the vehicle. This is accomplished by abutting a pair of slant bars next to the tires and by then securing the bars to the tires by a pair of adjustable bars. As a result, a cradle is formed about the tires, and is then attached to a conventional tow truck cable which includes a stabilizer to properly maintain the vehicle in a horizontal plane when being raised. While HARING discloses a frame which can be more easily negotiated in tight spaces, the apparatus requires manual assembly underneath the vehicle. Therefore, the operation is both time-consuming and may require more than one operator.
Finally, YOUNG BLOOD, U.S. Pat. No. 4,186,938, discloses a tow lift arrangement which requires attachment of a tow bar directly to the frame of the vehicle. The tow bar must be manually attached to the vehicle and requires precise alignment with the vehicle frame in order to place the ends of the tow bar in direct communication with holes in the frame. YOUNG BLOOD, as a result, also requires precise alignment and would need two operators to achieve alignment. Also, YOUNG BLOOD does not benefit from attaching a connection to a point where the suspension system of the vehicle can be used as a shock absorber.
In conclusion, prior art vehicle wheel lift devices require complex or difficult maneuvers of the tow truck to correctly align the vehicle lift system, or entail manual manipulation to securely connect the apparatus to the vehicle. Both of these problems are clearly overcome by the present invention.